Study: Bark beetles not a factor fast wildfire spread

Jan. 24, 2013

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It was a common theme in statements from both firefighters and public officials when the High Park Fire was scorching Larimer County: Dead trees killed by mountain pine beetles are responsible for the rapid spread and intensity of wildfires in Northern Colorado.

But a new study, echoing many studies before it, says that’s not true. The real culprit: climate change-fueled drought.

The study, co-authored by Colorado State University wildlife ecology professor Barry Noon and scientists at Clark University, the Xerces Society and the Geos Institute, shows that fire risk is tied primarily to drought conditions.

Removal of bark beetle-killed trees may reduce the risk for small wildfires, but not catastrophic crown fires that ravaged Colorado forests in 2012, the study concludes.

“Drought and high temperatures are likely the overriding factors behind the current bark beetle epidemic in the western United States,” said Xerces Society Executive Director Scott Hoffman. “Because logging and thinning cannot effectively alleviate the overriding effects of climate, it will do little or nothing to control these large-scale outbreaks.”

Similar studies conducted by the U.S. Forest Service and CSU have come to the same conclusion in the past, but policymakers and even Jeff Jahnke, former director of the Colorado State Forest Service, have said it’s clear bark beetles are a major player in wildfire spread.

“They don’t even listen to their own scientists,” Noon said, referring to policymakers and land managers who insist bark beetles play a major role in wildfires.

Bark beetle-devastated Rocky Mountain National Park has a fire management plan that relies on research that concludes the beetle has little effect on the spread of wildfire there, park officials said last year.

Jahnke, a longtime firefighter and then CSFS director, said in June the bark beetle is the biggest reason Larimer County’s forests burned in 2012.

The beetles, he said, “created red trees that are very dry and burn explosively.”

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But Noon said that’s not quite true.

“Here’s the issue — for a fire, you need two things: You need an ignition source, and you need fuel,” Noon said. “Certainly dead trees that still have brown needles on them are an ignition source. They won’t carry the fire in a catastrophic fashion because there’s insufficient fuel in the canopy of the trees. The fuel part of the trees are in the live canopies. That’s where all the biomass resides.”

Living trees burn just as fast and easily as dead trees in drought years.

“People don’t want to admit there’s a drought because the drought is driven by carbon dioxide buildup in the atmosphere,” Noon said. “It’s telling people something they don’t want to hear.”

The study also concludes that logging and thinning can lead to heightened insect activity by removing large, dead trees that are often used as habitat by species that prey on bark beetles. That could prolong bark beetle outbreaks because of a reduction in the beetles’ natural enemies.

The study, “Do Bark Beetle Outbreaks Increase Wildlfire Risks in the Central Rocky Mountains? Implications from Recent Research” was published Wednesday in the “Natural Areas Journal.”